A shipping container can be used for transporting machinery, equipment and produce. They are designed and built to carry heavy loads and support heavy loads, even when they are stacked on top of each other. They tolerate harsh environments when they are transported globally. Most shipping containers are made to the same standard measurements (8′ width, 20′, 35′, 40′ or 45′ length and 8′6″ or 9′6″ height). They can include top, side and bottom rails with interval stringers in between the top and bottom rails and doors at one end. As many as 30 interval stringers can be present in a 40′ container to help prevent delamination of the outer container coating from the container frame. As a result the containers can be structurally very strong and when empty can be stacked upon each other up to twelve high.
A drum, or more specifically a 55-gallon drum (or 44-gallon drum based on the imperial volume) is another commonly used container for shipping materials. A 55-gallon drum is 22.5 inches (572 mm) in diameter and 33.5 inches (851 mm) high as specified in ANSI MH2 and has a volume of approximately 208-liters. A 42 gallon (159 liter) and 25 gallon (95 liter) drum are also common size containers used for shipping. A drum shipping container can be closed-head or open-head. Closed-head drums are generally made of a steel cylinder with reinforcing rings to improve rigidity and durability. Bottom and top plates can be welded to the cylinder. The reinforcing rings are positioned at the bottom, one third, two thirds and top. The top plate has one 2-inch (50.8 mm) NPT and one ¾-inch (19 mm) NPT threaded holes or bungs. These are generally on opposite sides. This arrangement is echoed in many plastic drums of the same size. Various components can be mounted to the drum, such as drum pumps and bung mixers. They are commonly used for transporting oils, fuels and a variety of chemicals. Open-head drums are sealed by a concave inwards mechanical ring clamp that can make an airtight seal against a gasket. Top plates exist with standard bung holes. Open-head drums can be used to ship many non-volatile liquids as well as industrial powders (e.g., aluminum), beads (e.g., polystyrene) and granules (e.g., fertilizers).